From 2cbb06b561f500732de2214eb590149d0c4f3cf5 Mon Sep 17 00:00:00 2001 From: Brian Behlendorf Date: Tue, 17 Mar 2015 15:07:47 -0700 Subject: Restructure per-filesystem reclaim Originally when the ARC prune callback was introduced the idea was to register a single callback for the ZPL. The ARC could invoke this call back if it needed the ZPL to drop dentries, inodes, or other cache objects which might be pinning buffers in the ARC. The ZPL would iterate over all ZFS super blocks and perform the reclaim. For the most part this design has worked well but due to limitations in 2.6.35 and earlier kernels there were some problems. This patch is designed to address those issues. 1) iterate_supers_type() is not provided by all kernels which makes it impossible to safely iterate over all zpl_fs_type filesystems in a single callback. The most straight forward and portable way to resolve this is to register a callback per-filesystem during mount. The arc_*_prune_callback() functions have always supported multiple callbacks so this is functionally a very small change. 2) Commit 050d22b removed the non-portable shrink_dcache_memory() and shrink_icache_memory() functions and didn't replace them with equivalent functionality. This meant that for Linux 3.1 and older kernels the ARC had no mechanism to drop dentries and inodes from the caches if needed. This patch adds that missing functionality by calling shrink_dcache_parent() to release dentries which may be pinning inodes. This will result in all unused cache entries being dropped which is a bit heavy handed but it's the only interface available for old kernels. 3) A zpl_drop_inode() callback is registered for kernels older than 2.6.35 which do not support the .evict_inode callback. This ensures that when the last reference on an inode is dropped it is immediately removed from the cache. If this isn't done than inode can end up on the global unused LRU with no mechanism available to ZFS to drop them. Since the ARC buffers are not dropped the hottest inodes can still be recreated without performing disk IO. Signed-off-by: Brian Behlendorf Signed-off-by: Pavel Snajdr Issue #3160 --- module/zfs/arc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'module/zfs/arc.c') diff --git a/module/zfs/arc.c b/module/zfs/arc.c index 188086767..f9f0008c0 100644 --- a/module/zfs/arc.c +++ b/module/zfs/arc.c @@ -158,8 +158,8 @@ static kmutex_t arc_reclaim_thr_lock; static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */ static uint8_t arc_thread_exit; -/* number of bytes to prune from caches when at arc_meta_limit is reached */ -int zfs_arc_meta_prune = 1048576; +/* number of objects to prune from caches when arc_meta_limit is reached */ +int zfs_arc_meta_prune = 10000; typedef enum arc_reclaim_strategy { ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */ @@ -5607,7 +5607,7 @@ module_param(zfs_arc_meta_limit, ulong, 0644); MODULE_PARM_DESC(zfs_arc_meta_limit, "Meta limit for arc size"); module_param(zfs_arc_meta_prune, int, 0644); -MODULE_PARM_DESC(zfs_arc_meta_prune, "Bytes of meta data to prune"); +MODULE_PARM_DESC(zfs_arc_meta_prune, "Meta objects to scan for prune"); module_param(zfs_arc_grow_retry, int, 0644); MODULE_PARM_DESC(zfs_arc_grow_retry, "Seconds before growing arc size"); -- cgit v1.2.3